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Abstract

The adsorption or absorption of 4-(phenylazo)benzoic acid onto polyphenolic precipitates shows promise as a model system for adsorption and absorption of hydrophobic waste compounds. Using 1 mM of phenol under conditions used for enzyme conversion with soybean peroxidase and hydrogen peroxide (1 U/mL soybean peroxidase and 1.5 mM hydrogen peroxide) two conditions of ad/absorption were characterized with the Langmuir isotherm. These conditions, hereby referred to as static and dynamic, consist of ad/absorption onto phenolic precipitates either during enzymatic conversion of phenol (dynamic) or after enzymatic conversion of phenol (static). Both the dynamic and static systems showed high affinity for phenolic precipitates with Langmuir association constants of 0.088 and 0.13 L/mg, respectively. The dynamic system showed a 3-fold greater maximum ab/adsorption capacity than the static system, 51 and 16 mg/g, respectively. During the characterization process the pKa of 4-(phenylazo)benzoic acid was determined to be 2.45 and the possibility of enzyme-catalyzed reductive splitting of the azo-bond was studied. The characterization of the ad/absorption of 4-(phenylazo)benzoic acid onto phenolic precipitates showed good fit with the Langmuir isotherm. This opens the possibility of characterization of other adsorption systems with phenolic precipitates for the purpose of expanding the scope of the SBP enzymatic process as a waste-water treatment method beyond its direct substrates.